Improving the sprayability of polychloroprene contact by shearing in microfluidizer

ABSTRACT

Polychloroprene contact adhesive is made by mixing polychloroprene, tackifier, metallic oxide, antioxidants and organic solvent. The contact adhesive is sheared for reducing its ASTM D 1084 Saybolt viscosity by 10 percent or more. Shearing improves the sprayability of the polychloroprene contact adhesive. It makes it more uniform and reduces its viscosity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to shearing polychloroprene contact adhesives forimproving their sprayability. This invention particularly relates tomaking polychloroprene contact adhesives sprayable from aerosolcontainers.

2. Description of the Related Art

Polychloroprene contact adhesive, when coated on two materials adheresto itself upon contact, after drying. Polychloroprene contact adhesiveshave been formulated in both solvent and water-based systems. Thematerials joined together can be the same or different and include wood,plastic laminates, paper, various materals such as glass, carbon fiber,concrete, ceramics, and metals such as iron, steel, and aluminum.

The choice of the particular type of polychloroprene will depend on theproperties (e.g. flammability, oil resistance, toughness, extensibility,crystallization rate, resistance to crystallization, etc.) required inthe contemplated end use.

Polychloroprene contact adhesives are commercially formulated withtackifiers, metallic oxide and antioxidants. Additionally, the use ofcopolymers of chloroprene, 2-chloro-1,3-butadiene, and alkylacrylates ormethacrylates along with homopolymers of chloroprene have been found toimpart high temperature bonding characteristics to polychloroprenecontact adhesives. The relative amounts of the particular componentsemployed will vary over a wide range depending upon the specificcomponents as well as the desired end use.

Commercially available tackifiers for polychloroprene contact adhesivesinclude natural and modified rosins, polyterpene resins, phenolicresins, phenolic modified terpene resins, and aliphatic petroleumhydrocarbon resins.

Metallic oxide, such as magnesium and zinc oxide, serves as acidacceptors by neutralizing the hydrochloric acid which is released uponthe aging of polychloroprene, thereby minimize the deterioration ofmaterials that come into contact with the polychloroprene contactadhesives. They serve, furthermore, as curing agents for thepolychloroprene, thereby increasing the tensile strength of theresulting adhesive bonds, and also aid in the room temperaturecrosslinking.

The antioxidant prevents embrittlement and discoloration. The followingantioxidants have been disclosed as suitable for use in formulatingpolychloroprene contact adhesives: phenyl-alpha-naphthylamine,phenyl-beta-naphthylamine, phenyl-beta-naphthalene, and2,2,'-methylene-bis (4-methyl-6-tertiary butyl-phenol).

Small volume applications of polychloroprene contact adhesives areconveniently applied by aerosol spraying. An aerosol sprayhead nozzlestructure is disclosed which enables the formulation of aerosoladhesives based on soluble polychloroprene that, in turn, producedapproximately two and one-half times the area coverage as compared tothe best commercially available aerosol fan sprayhead. The sprayheadpermitted an aerosol solids level as high as 11.1 percent, which wouldprovide enough adhesive in a 16 fluid ounce (480 cubic centimeters)container to cover two surfaces of an area of 99.3 square feet (9.23square meters), while the best commercially available aerosol fansprayhead was able to produce an acceptable fan spray pattern at levelsno higher than 4.4 percent aerosol solids using the same adhesiveformulation, which would provide an amount of adhesive in the same sizecontainer sufficient to cover two surfaces of an area of only about 39.4square feet (3.66 square meters). (U.S. Pat. No. 4,401,272)

The improved nozzle structure permits adhesives in solution to besprayed in an acceptable pattern at typical aerosol container pressuresof between approximately 20 psi (0.14 megapascals) and 100 psi (0.69megapascals), as opposed to the approximately 2,000 psi (13.8megapascals) necessary when such solutions of polychloroprene contactadhesives are sprayed using airless spray gun equipment. It is thoughtthat this ability to spray at low pressures and the dramatic differencein pressures is at least partially attributable to the fact that inaerosol applications the propellant is in solution and a portion of thepropellant is sprayed along with the adhesive solution.

The spray pattern produced by this disclosed spray head has not beencompletely uniform in that areas of light coverage and sharply defined,stringy margins are produced, and the spray nozzle cannot adequatelycope with normal milling variations of the rubber and variations in thesolids content of the adhesive solution.

It is disclosed that a restriction in the flow path of polychloropreneadhesive upstream of the spray nozzle increases the uniformity of afan-shaped spray pattern and the tolerance of the sprayhead for millingvariations in polychloroprene. The restriction can be a single orificeor a plurality of orifices.

Spray patterns are disclosed for polychloroprene contact adhesivesprayed from an aerosol container with and without an orifice. Dimethylether is used as the propellant. The polychloroprene adhesive is 11.1 wt% solids. It is sprayed from above onto a horizontal from a containerheld at approximately 45 degrees with the nozzle opening approximately 6inches (150 mm) from the surface. Spray pattern is distinguished bysharply defined and stringy margins on both ends, and areas of lightcoverage toward the ends. The spray pattern with the restriction ischaracterized as having an absence of stringy margins and much lesssevere areas of light coverage. A sample of the spray pattern was driedand cut into five equal sections, each comprising one-fifth of thepattern transverse to the direction of the sprayhead motion. Followingis the amount of polychloroprene contact adhesive on each sectionexpressed as the percentage of the total polychloroprene adhesive on thesample.

    ______________________________________                                                    Adhesive on One-Fifth of Spray Pattern Width                                  (% of Total)                                                      Orifices    Away from Container --- Toward Container                          ______________________________________                                        None        34.3    32.4    12.7    7.8  12.5                                 One Orifice 19.1    12.4    20.2   18.0  30.3                                 Two Orifices                                                                              11.0    11.0    15.1   39.7  23.3                                 Three Orifices                                                                            25.8    16.5    18.6   13.4  25.8                                 ______________________________________                                    

A sprayable adhesive composition based on nonionic neoprene latex isdisclosed. Sprayability, including the capability for application byaerosol spraying, is imparted in the adhesive by providing a nonionicsurfactant in the composition and by avoiding ingredients that wouldcause coalescence or thickening. The addition of a nonionic surfactantprovides for an effective adhesive formulation without use of an alkaliand enables preparation of the formulation using a modified "one-shothigh-shear mix" technique, resulting in a sprayable composition withminimized water content. A nonionic surfactant is essential to providinga composition that may be applied by aerosol spraying withoutcoagulating or clogging the spray equipment or canister. (U.S. Pat. No.5,444,112)

The components are combined under agitation to form a dispersion that isthen filtered to remove particles that could cause coagulation andclogging up of spray equipment or containers. The starting nonionicneoprene latex is first combined with a liquid surfactant, and the twoare thoroughly mixed. The remaining ingredients including resin, zincoxide, and antioxidant are then added to the dispersion in dry formunder high shear as by being agitated in a Silverson mixer at a speed of3,445 rpm. The dispersion is then subjected to filtration to remove anycoagulated solids that might cause clogging.

Depending on the amount of adhesive being used for a particular type ofapplication, the adhesive prepared as described above may be packaged inself-contained, pressurized aerosol cans or canisters or in drumsequipped with a pressurized air system and a remote spray gun.

There is a need for a polychloroprene contact adhesive that can besprayed from an aerosol container in a uniform spray pattern. There isalso a need for a polychloroprene adhesive that can be formulated tohave not less than 15 weight percent (wt %) solids. There is a furtherneed for a polychloroprene contact adhesive that can be sprayed from anaerosol container with valves and nozzles that are commerciallyavailable.

SUMMARY OF THE INVENTION

It has now been discovered that polychloroprene contact adhesives can besheared for making them sprayable from aerosol containers in uniformspray patterns. Shearing for reducing the Stormer ASTM D 1084 viscosityby at least 10% and preferably by at least 15% and most preferably by atleast 20%, while holding the solids content constant, permits theformulation of polychloroprene contact adhesive to solids contents of 15weight percent or greater. Polychloroprene contact adhesive can besheared in accordance with this invention for spraying from aerosolcontainers through commercially available spray heads and nozzles. Thespray pattern remains substantially uniform as all of the contents ofthe aerosol container is sprayed.

DETAILED DESCRIPTION OF THE INVENTION

Polychloroprene contact adhesive of the following formulation is usedfor illustrating the shearing of this invention. Samples 1-12 areportions of this formulation that have been subjected to shearing asshown on Tables 1 and 2. The spraying characteristics of Samples 1-12from aerosol containers with different nozzle openings and from apressurized system with a remote spray gun are shown on Tables 3 and 4.The bonding characteristics of Samples 1-12 are shown on Tables 5 and 6.Bonding characteristics of commercially available contact adhesives areshown on Table 7.

    ______________________________________                                                             Grams Pounds                                             ______________________________________                                        Chloroprene/Methacrylic Acid Copolymer                                                               274,042 603.6                                          Polychloroprene (BP223)                                                                              58,234  128.3                                          Polychloroprene (BP213)                                                                              10,277  22.6                                           Alkylphenolic Resin (HJR 1367)                                                                       196,968 433.9                                          Terpene Phenolic Resin (SP 553)                                                                      42,819  94.3                                           Magnesium Oxide        37,681  83.0                                           Antioxidant (WINGSTAY L)                                                                             5138    11.3                                           Hexane                 642,292 1414.7                                         Acetone                591,585 1303.1                                         Toluene                236,634 521.2                                          Cyclohexane            121,697 268.1                                          Pentane                98,034  215.9                                          Water                  2,789   6.14                                           ______________________________________                                    

Chloroprene/Methacrylic Acid Copolymer used in this formulation iscommercially available from E. I. du Pont de Nemours & Co. (Inc.),Wilmington Del. 19896, under the brand name NEOPRENE AF. Polychloroprene(BP223) and Polychloroprene (BP213) are commercially available fromMobay Corporation, a Bayer USA Inc. Company, Plastics and RubberDivision, Pittsburgh, Pa. 15205-9741, under the product names BP223 andBP213, respectively. Alkylphenolic Resin (HJR 1367) and Terpene PhenolicResin (SP 553) are commercially available from Schenectady Chemicals,Inc., Box 1046, Schenectady, N.Y. 12301, under the product names HRJ1367 and SP 553, respectively. Magnesium Oxide is commercially availablefromPremier Services Corporatio, 7251 Engle Road, Suite 4125, MiddleburgHeights, Ohio 44130, under the brand name MAGOX® Antioxidant (WINGSTAYL)is commercially available from Good Year Chemicals, Akron, Ohio 44316,under the brand name WINGSTAY® L.

                  TABLE 1                                                         ______________________________________                                        Viscosity Reduction by Increasing Pressure                                    Samples                                                                             Passes  Pressure Viscosity                                                                            Molecular                                       #     #       psi.     sec.   Weight Polydispersivity                         ______________________________________                                        1     0       NA       21.0   340,000                                                                              2.5                                      2     1        5,000   18.0   310,000                                                                              1.9                                      3     1       10,000   17.6   265,000                                                                              1.8                                      4     1       15,000   17.4   245,000                                                                              2.0                                      10    1       20,000   17.0   255,000                                                                              2.0                                      11    1       25,000   17.3   230,000                                                                              1.8                                      12    1       28,000   16.6   220,000                                                                              1.7                                      ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Viscosity Reduction With Multiple Passes                                      Samples                                                                             Passes  Pressure Viscosity                                                                            Molecular                                       #     #       psi.     sec.   Weight Polydispersivity                         ______________________________________                                        4     1       15,000   17.4   245,000                                                                              2.0                                      5     2       15,000   16.5   230,000                                                                              1.5                                      6     3       15,000   15.8   190,000                                                                              1.6                                      7     4       15,000   15.6   175,000                                                                              1.5                                      8     5       15,000   15.7   170,000                                                                              1.4                                      9     6       15,000   15.4   155,000                                                                              1.4                                      ______________________________________                                    

Viscosity of Samples 1-12 was reduced by shearing polychloroprenecontact adhesive in a Microfluidizer® Processor, model M-210,commercially available from Microfiuidics International Corporation, 30Ossipee Road, Newton Mass. 02164-9101. The amount of shear isproportional to the pressure applied during the operation of theMicrofiuidizer Processor. Additional shear can be imparted by passingthe contact adhesive through the Microfiuidizer Processor additionaltimes.

Viscosity was determined with a Stormer Viscometer under Test Method Cof American Society for Testing and Materials (ASTM) D 1084, StandardTest Methods for Viscosity of Adhesives. A 200 gram weight was used.

Molecular weight was determined by gel permeation chromatography forSamples 1-12. Results are the average of two runs. Samples were driedfor evaporating solvents. Solids were dissolved in reagent grade tolueneto give a 0.3 weight percent (wt %) solution. Solutions were filteredthrough a 0.45 micrometer (μm) filter. The gel permeation chromatography(GPC) system used for determining these molecular weights iscommercially available from the Waters Corporation, 34 Maple Street,Milford, Mass., 01757. This GPC system includes a Waters 410Differential Refractometer with shelf assembly and column heater module,(PN WAT023995), Waters 717 Plus Autosampler, (PN WAT078900), Waters 600Multisolvent delivery system, (PN WAT062710), Waters Millenium® 2010Workstation (PN WAT042862), including the GPC Chromatography Manager,(PN WAT038977), Waters HR Stratagel (5μm styrene-divinylbenzeneparticles) GPC columns, HR 5, (PN WAT044227), HR4, (PN WAT044224), HR3(PN WAT044221), HR1 (PN WAT044233). Polystyrene standards ranging from2,399,254 to 28,517 molecular weight were used for calibration.Conditions for the GPC are as follows:

Mobile Phase: Toluene at 1 milliliter per minute

Detector: Differential refractive index at 32X

Temperature: 70° C. oven, 50° C. detector

Columns: HR 5, 4, 3, and 1 Stratagel

Molecular weight reported in Tables 1 and 2 is the weighted averagemolecular weight. It is believed that large molecules contribute more tothis molecular weight determination than small molecules.

Polydispersivity is determined from measurements made with this GPCsystem. It is believed that polydispersivity is a measure of the rangeof molecular weights and their concentration in a test sample.

Aerosol spray containers were filled with 234.3 grams of Samples 1-12along with 191.7 grams of dimethyl ether as a propellant. The solidscontent of these aerosol containers was 15 percent by weight of thecontents of the aerosol container.

Samples 1-12 were also sprayed from an air atomized spraying system thatis commercially available from Binks Manufcturing Company, 9201 WestBelmont Avenue, Franklin, Ill., 60131.

                  TABLE 3                                                         ______________________________________                                        Spray Characteristics of Contact Adhesive                                     Sheared at Increasing Pressures                                                     Viscosity                                                               Samples                                                                             Stormer              Aerosol    Atomized                                #     sec.     Polydispersivity                                                                          1    2    3    psi.                                ______________________________________                                        1     21.0     2.5         VB   VB   VB   105                                 2     18.0     1.9         G    VB   VB   90                                  3     17.6     1.8         G    VB   VB   76                                  4     17.4     2.0         G    VB   VB   74                                  10    17.0     2.0         VG   VB   VB   72                                  11    17.3     1.8         VG   VB   VB   72                                  12    16.6     1.7         E    VB   VB   72                                  ______________________________________                                         VB  No lace pattern                                                           B  Lace pattern with height between 1/4 and 1/2 inches                        G  Lace pattern with height between 1/2 and 1 inches                          VG  Lace pattern with height between 1 and 2 inches                           E  Lace pattern with height between 2 and 4 inches                       

                  TABLE 4                                                         ______________________________________                                        Spray Characteristics of Contact Adhesive                                     Sheared by Additional Passes at 15,000 psi                                    Samples                                                                             Viscosity            Aerosol    Atomized                                #     sec.     Polydispersivity                                                                          1    2    3    psi.                                ______________________________________                                        4     17.4     2.0         G    VB   VB   74                                  5     16.5     1.5         VG   VB   B    72                                  6     15.8     1.6         E    B    VG   66                                  7     15.6     1.5         E    VG   VG   66                                  8     15.7     1.4         E    VG   VG   64                                  9     15.4     1.4         E    E    E    60                                  ______________________________________                                         VB  No lace pattern                                                           B  Lace pattern with height between 1/4 and 1/2 inches                        G  Lace pattern with height between 1/2 and 1 inches                          VG  Lace pattern with height between 1 and 2 inches                           E  Lace pattern with height between 2 and 4 inches                       

                  TABLE 5                                                         ______________________________________                                        Bonding Characteristics of Contact Adhesive                                   Sheared at Increasing Pressures                                                                     Deadload                                                Samples                                                                              Viscosity             Plug 48 hours                                                                             2 weeks                              #      sec.     Polydispersivity                                                                           psi  °C.                                                                           °C.                           ______________________________________                                        1      21.0     2.5          80   110    130+                                 2      18.0     1.9          75   100    130+                                 3      17.6     1.8          75   100    130+                                 4      17.4     2.0          80   100    130                                  10     17.0     2.0          95   100    130+                                 11     17.3     1.8          85   100    120                                  12     16.6     1.7          105  100    130+                                 ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Bonding Characteristics of Contact Adhesive                                   Sheared by Additional Passes at 15,000 psi                                                          Deadload                                                Samples                                                                              Viscosity             Plug 48 hours                                                                             2 weeks                              #      sec.     Polydispersivity                                                                           psi  °C.                                                                           °C.                           ______________________________________                                        4      17.4     2.0           80  100    130                                  5      16.5     1.5           95  100    120                                  6      15.8     1.6          105  90     115                                  7      15.6     1.5          100  90     110                                  8      15.7     1.4          100  90     110                                  9      15.4     1.4          100  90     110                                  ______________________________________                                    

Plug testing provides an indication bond strength between laminate andnon-metallic substrates, such as particleboard, plywood or laminate.Laminate measuring 2.5 inches wide and 7.75 inches long is bonded toparticleboard measuring 2.5 inches wide and 7.75 inches long withSamples 1-12. The test specimens are cured in an oven at 75° F. for 48hours. After curing, the laminate is cut through to the particle boardat three spaced apart locations along the test specimen with a 1.75 inchoutside diameter hole saw. Using the pilot hole made in making the 1.75inch cut, The particle board is cut through to the laminate with a 1inch outside diameter hole saw. A 1 inch outside diameter washer with abolt extending through the washer and pilot hole is placed against theparticle board. A force is applied to the bolt extending through thepilot hole at 2 inches per minute. The force at which the laminateseparates from the particleboard is recorded as the plug strength. Plugstrengths of 50 psi or greater are considered as commerciallyacceptable. Plug strengths of 100 psi or greater are considered asexcellent.

Deadload testing provides an indication of the load bearing capabilityof laminate bonded to non-metallic substrates, such as particleboard,plywood or laminate. Laminate measuring 2 inches wide and 3.5 incheslong is bonded to particleboard measuring 2 inches wide and 2.5 incheslong with Samples 1-12. This leaves laminate measuring 1 inch extendingbeyond the end of the particleboard at the top of the test specimen. Thetest specimens are cured in an oven at 75° F. for 48 hours and 2 weeks.After curing, the laminate is cut through to the particle board 1 inchfrom the bottom of the test specimen. This leaves laminate measuring 2inches wide and 2 inches long bonded to particleboard measuring 2 incheswide and 2 inches long. The test specimen is hung in an oven by a holedrilled through the laminate extending beyond the particleboard at thetop of the specimen. A 7.5 pound weight is hung from a hole drilledthrough the laminate and particle board below the cut made through thelaminate 1 inch from the bottom of the test specimen. The temperature inthe oven is increased from 50° to 130° C. in 10° C. increments every 15minutes. The temperature at which the laminate releases from theparticleboard is recorded as the deadload temperature.

Samples 1-12 passed corner and edge lift and peel tests.

Contact adhesive formulated with the substitution of AlkylphenolicResin, commercially available under the product name FRJ-551, fromSchenectady Chemicals, Inc., for Alkylphenolic Resin (HRJ-1367) inSamples 1-12, did not retain its deadload strength after shearing. In adeadload test, laminate separated from substrate at 70° C., 30°-60° C.below the temperature that samples 1-12 separated. Alkylphenolic Resin(HRJ-1367) is known commercially to have a higher heat resistance thanAlkylphenolic Resin (FRJ-551).

                  TABLE 7                                                         ______________________________________                                        Bonding Characteristics of Commercially Available Contact Adhesive                                 Deadload                                                 Samples                Plug    48 hours                                                                             2 weeks                                 #      Elastomer       psi     °C.                                                                           °C.                              ______________________________________                                        C-1    Polychloroprene 80      100    130                                     C-2    Styrene Butadiene Rubber                                                                      50      70     70                                      C-3    Styrene Butadiene Rubber                                                                      110     90     90                                      C-4    Styrene Butadiene Rubber                                                                      75      70     70                                      C-5    Styrene Isoprene Styrene                                                                      125     50     50                                      C-6    Styrene Isoprene Styrene                                                                      95      90     80                                      C-7    Styrene Isoprene Styrene                                                                      65      90     90                                      ______________________________________                                    

Sample 12 was charged into an aerosol container with dimethyl ether as apropellant. The solids content in the container was 15 percent by weightof the contents of the container. The entire contents of aerosolcontainers were sprayed and spray patterns were made on paper when thecan was full, at 100 percent by volume of capacity, and at 50 and 10percent of capacity. A sample of the spray pattern was dried and cutinto four equal sections, each comprising one-fourth of the patterntransverse to the direction of the sprayhead motion. Following is theamount of polychloroprene contact adhesive on each section expressed asthe percentage of the total polychloroprene adhesive on the sample. Thespray pattern of Sample 12 is compared with Sample C-1. U.S. Pat. No.4,401,272 is disclosed on the label of Sample C-1. The height of thespray pattern on Sample 12 remained about the same as the contents ofthe aerosol container was sprayed. The height of the spray pattern ofSample C-12 diminished.

    ______________________________________                                        Sample 12                                                                     Capacity        Adhesive on One-Fourth of Spray Pattern Width                 Percent Height  (% of Total)                                                  by Vol. Inches  Away from Container --- Toward Container                      ______________________________________                                        100     23/16   24.3     25.7    25.0   25.0                                  50      25/16   25.2     24.4    25.2   25.2                                  10      25/16   24.5     25.2    24.5   25.8                                  ______________________________________                                    

    ______________________________________                                        Sample C-1                                                                    Capacity        Adhesive on One-Fourth of Spray Pattern Width                 Percent Height  (% of Total)                                                  by Vol. Inches  Away from Container --- Toward Container                      ______________________________________                                        100     17/8    25.8     24.2    25.0   25.0                                  50      19/16   22.0     25.0    28.0   25.0                                  10      13/8    23.0     24.0    27.0   26.0                                  ______________________________________                                    

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty that reside in the present invention,including all features that would be treated as equivalents thereof bythose skilled in the art to which this invention pertains.

We claim:
 1. A method of making a contact adhesive, comprising:mixingchloroprene/methacrylic acid copolymer, polychloroprene, magnesiumoxide, tackifier, antioxidant, organic solvent, and water for making acontact adhesive, and shearing the contact adhesive in a microfluidizerfor reducing its ASTM D 1084 Saybolt viscosity by 10 percent or more,while maintaining the solids concentration constant at a level of notless than 15 weight percent.
 2. The method of claim 1 wherein thecontact adhesive is sheared for reducing its ASTM D 1084 Sayboltviscosity by 15 percent or more.
 3. The method of claim 1 wherein thecontact adhesive is sheared for reducing its ASTM D 1084 Sayboltviscosity by 20 percent or more.
 4. A method of making a contactadhesive, comprising;mixing chloroprene/methacrylic acid copolymer,polychloroprene, alkylphenolic resin, terpene phenolic resin, magnesiumoxide, antioxidant, hexane, acetone, toluene, cyclohexane, pentane, andwater for making a contact adhesive, and shearing the contact adhesivein a microfluidizer for reducing its ASTM D 1084 Saybolt viscosity by 10percent or more, while maintaining the solids concentration constant ata level of not less than 15 weight percent.
 5. The method of claim 4wherein the contact adhesive is sheared for reducing its ASTM D 1084Saybolt viscosity by 15 percent or more.
 6. The method of claim 4wherein the contact adhesive is sheared for reducing its ASTM D 1084Saybolt viscosity by 20 percent or more.